How do I change the dimensioning line weight of the measuring tool. It is so large that it covers what I am trying to measure.
By "dimensioning line weight of the measuring tool" do you mean the thickness of the line?
If yes, you can decrease the thickness of the line from the Dimension line properties window.
For that, select the dimension line and then right click on it.
Select properties from the drop down and change the thickness under the Appearance tab.
Check the screenshot below:
After changing the thickness, check the box for "Make Properties Default" and click OK to save settings.
So the next time you use measuring tool, you do not have to change the thickness.
Let us know if you have any questions or if you are referring to something else.